Separating layer recycling strategy for continuous fiber reinforced thermo-sets based on thermally expanding particles

Fiber-plastic composites with a thermosetting matrix are considered to have only limited recyclability. Either the high density-specific mechanical properties of the material are lost in the recycling process or the recycling processes are associated with very high costs, so that implementation is not economically worthwhile. A new approach is the reuse of continuous fiber reinforced laminate layers separated from a composite. In the present work, the extent to which laminate layers can be made separable from a thermosetting fiber-plastic composite was investigated. The separation is based on the volume increase mechanism of thermally expanding particles (TEP) introduced into the polymeric matrix of a laminate layer. Heating leads to expansion of the particles. As a result, the laminates can be separated. Glass fiber reinforced epoxy resin laminates with TEP in the separating matrix layer were fabricated and tested using hand lay-up techniques. Using the double cantilever beam test, it was determined that the force required for separation is drastically reduced with increasing TEP mass fraction. In addition, the extent to which the thermally expanding particles affect the mechanical properties of the laminates was tested. Through the 45° tensile test, it was determined that loads not parallel to one of the fiber directions have a negative effect on tensile strength and tensile stiffness.